Image Adjusting Apparatus and Associated Method

ABSTRACT

An image adjusting method for extending vertical blanking intervals of an image signal is provided. Using the image adjusting method, an adjusted image signal is synchronized with an image signal before the adjustment to prevent image delay. The image adjusting method comprises providing a first image signal having a first data enable signal, wherein the first data enable signal has a first data enable duration; and generating a second data enable signal having a second data enable duration. The first and second data enable durations correspond to a same image frame of an image signal, and the second data enable duration substantially overlaps the first data enable duration.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This patent application is based on a U.S. provisional patentapplication No. 61/152,275 filed on Feb. 13, 2009.

FIELD OF THE INVENTION

The present invention relates to an image adjusting apparatus and anassociated method, and more particularly, to an image adjustingapparatus and an associated method for extending vertical blankingintervals of an image signal.

BACKGROUND OF THE INVENTION

In the three-dimensional (3D) stereo display technology, the 3D stereodisplay associated with a time sequence is considered as being quitemature. That is, images of the left eye and the right eye arealternately displayed on the basis of a time sequence so that the eyesof a viewer perceive the left-eye images and the right-eye imagesalternately. More particularly, the left eye of the viewer onlyperceives the left-eye images and the right eye of the viewer onlyperceives the right-eye images. For example, a pair of stereo glasses,having a left-eye shutter and a right-eye shutter, associated with adisplay capable of alternately displaying the left-eye images and theright-eye images, can provide 3D stereo images to the viewer.

FIG. 1 shows a schematic diagram of timing control of stereo imagesdisplayed by an LCD display and a pair of stereo glasses of the priorart. As shown, the LCD display alternately displays left-eye images andright-eye images. Since the LCD display is a hold-type display, each ofpixels of the LCD display displays current pixel data continuouslybefore being updated. Therefore, as shown in the diagram, during aninterval in which a display image of the LCD display is updated with aleft-eye image, the display image (e.g., a display image of a time pointTa illustrated at the bottom of FIG. 1) of the LCD display actuallycontains not only an updated left-eye image, but also a right-eye imagethat is not yet updated. Upon entering a vertical blanking interval, thedisplay image of the LCD display is completely updated with the updatedleft-eye image (e.g., a display image of a time point Tb illustrated atthe bottom of FIG. 1). Likewise, during an interval in which the displayimage of the LCD display is updated with a right-eye image, the displayimage (e.g., a display image of a time point Tc illustrated at thebottom of FIG. 1) of the LCD display actually contains not only anupdated right-eye image, but also a left-eye image that is not yetupdated. Upon entering a vertical blanking interval, the display imageof the LCD display is completely updated with the updated right-eyeimage (e.g., a display image of a time point Td illustrated at thebottom of FIG. 1).

In order to avoid crosstalk, the pair of stereo glasses is onlycorrespondingly switched to an open state during vertical blankingintervals. More specifically, the left-eye shutter of the pair of stereoglasses is opened during the vertical blanking intervals after theleft-eye images have been updated, and when the current display imagebegins to be updated with the right-eye images, both of the left-eye andright-eye shutters of the stereo glasses are closed. Similarly, theleft-eye shutter of the stereo glasses is opened during the verticalblanking intervals after the right-eye images have been updated, andwhen the current display image begins to be updated with the right-eyeimages, both of the left-eye and right-eye shutters of the stereoglasses are closed.

It is apparent from the foregoing description that, when viewing stereoimages with a pair of stereo glasses, the images can only be perceivedduring vertical blanking intervals, which are rather short in a commonimage signal. Under such circumstances, since intervals that a viewersees the images are extremely short, not only the viewer feels theimages have inadequate brightness, but also an intended stereo effectmay not be achieved as a result of left and right images of the stereoimages appear as separate images for that the left and right images failto form visual persistence in the viewer's brain. In order to provide asolution to above issue, the vertical blanking intervals need beextended to prolong intervals in which the stereo glasses are switchedto an open state. In the prior art, to increase the vertical blankinginterval, pixel data of an image signal is first written into atemporary memory, and is then read out from the memory according to arelatively faster read clock to generate an adjusted image signal.Through such approach, each data enable duration of a vertical dataenable signal is reduced from reading the pixel data with the relativelyfaster reading clock, while a frame cycle of the adjusted image signalremains unchanged, so that the vertical blanking interval is extended asdesired.

FIG. 2 shows a timing diagram of a vertical data enable signal of animage signal, before and after extending the vertical blanking intervalwith the prior art. A vertical data enable signal VDE₁ in the unadjustedimage signal includes a plurality of vertical data enable durations,each of which indicates a position of pixel data corresponding to animage frame in the unadjusted image signal. A vertical data enablesignal VDE₂ in the adjusted image signal similarly includes a pluralityof vertical data enable durations, each of which indicates a position ofpixel data corresponding to an image frame in the adjusted image signal.As shown in FIG. 2, a rising edge of a vertical data enable durationVDE₂ _(—) _(n−1) of an (n−1)^(th) frame of the vertical data enablesignal VDE₂ in the adjusted image signal is aligned with a rising edgeof a vertical data enable duration VDE₁ _(—) _(n) of an n^(th) frame ofthe vertical data enable signal VDE₁ in the unadjusted image signal—itmeans the adjusted image signal falls one frame cycle behind theunadjusted image signal. Thus, the prior approach for increasing thevertical blanking intervals leads to delaying an adjusted image signalby at least one frame cycle compared to an unadjusted image signal, suchthat the delay in the adjusted image signal leads to in signal delay incertain applications. For example, in an application oftelevision/computer game display, score performance of the user may beundesirably affected due to message hold-up from the delay of theadjusted image signal.

SUMMARY OF THE INVENTION

One of the objectives of the invention is to provide an image adjustingapparatus and an associated method for extending vertical blankingintervals of an input image signal, so as to synchronize an adjustedimage signal with an unadjusted image signal to prevent image delay.

To achieve the foregoing objective, an image adjusting method accordingto the invention comprises: providing a first image signal having afirst data enable signal, wherein the first data enable signal has afirst data enable duration; and generating a second data enable signalincluding a second data enable duration. The first and second dataenable durations correspond to a same image frame of the first imagesignal, and the second data enable duration substantially overlaps thefirst data enable duration.

In the image adjusting method according to one embodiment of theinvention, the second data enable duration is smaller than the firstdata enable duration, and a start point of the second data enableduration falls behind a start point of the first data enable duration.

An image adjusting apparatus is further provided according to theinvention to extend vertical blanking intervals of a first image signal.The first image signal comprises a first data enable signal and pixeldata of an image frame, and the first data enable signal includes afirst data enable duration. The image adjusting apparatus comprises amemory for storing the pixel data of the first image signal, and a dataenable signal generator for generating a second data enable signal forcontrolling the timing which the memory outputs the pixel data. Thesecond data enable signal includes a second data enable duration. Thefirst and second data enable durations correspond to the image frame ofthe first image signal, and the second data enable durationsubstantially overlaps the first data enable duration.

In the image adjusting apparatus according to one embodiment of theinvention, the data enable signal generator generates the second dataenable signal according to a predetermined time, a frame cycle and aread clock.

According to another embodiment of the invention, the image adjustingapparatus further comprises: a detector, for detecting a first referencepoint of the first data enable signal to generate a first detectionsignal, and detecting a second reference point of the second data enablesignal to generate a second detection signal; an adjustment valuegenerator, for generating an adjustment value according to the first andsecond detection signals; and a clock generator, for generating a readclock and adjusting the read clock according to the adjustment value.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more readily apparent to thoseordinarily skilled in the art after reviewing the following detaileddescription and accompanying drawings, in which:

FIG. 1 is a schematic diagram of timing control of stereo imagesdisplayed by an LCD display and a pair of stereo glasses of the priorart;

FIG. 2 is a timing diagram of vertical data enable signals of an imagesignal, before and after extending the vertical blanking interval withthe prior art;

FIG. 3 is a block diagram of an image adjusting apparatus according toone embodiment of the invention;

FIG. 4 is a timing diagram of vertical data enable signals of an imagesignal, before and after extending the vertical blanking interval withan image adjusting apparatus according to the invention;

FIG. 5 is a functional block diagram of an adjustment value generator inthe image adjusting apparatus according to an embodiment of theinvention;

FIG. 6 is a timing diagram of a vertical data enable signal of aninput/output signal when the read clock is too fast; and

FIG. 7 is a timing diagram of vertical data enable signals of input andoutput image signal according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an image adjusting apparatus forextending a vertical blanking interval of an image signal, so as tosubstantially synchronize an adjusted image signal with an unadjustedimage signal to prevent image delay. With reference to FIG. 3 showing ablock diagram of an image adjusting apparatus according to oneembodiment of the invention, an image adjusting apparatus 300 comprisesa memory 310, a data enable signal generator 320, a detector 330, anadjustment value generator 340, and a clock generator 350. The imageadjusting apparatus 300 is for adjusting vertical blanking intervals ofan input image signal Vin to output an output image signal Vout. Theinput image signal Vin comprises a vertical data enable signal VDEin andimage data, and the vertical data enable signal VDEin includes aplurality of data enable durations, each of which indicates a positionof pixel data corresponding to a frame in the image data. The outputimage signal Vout comprises a vertical data enable signal VDEout andimage data. The memory 310 is for temporarily storing pixel data of theinput image signal Vin. In practice, pixel data corresponding to theframes of the input image data Vin is sequentially written into thememory 310 according to the data enable signal VDEin and a write clockWCLK. More specifically, pixel data corresponding to each frame of theinput image signal Vin is located within a data enable duration of thevertical data enable signal VDEin, and the corresponding pixel data,under the control of the write clock WCLK, is written into the memory310 during the data enable duration.

The data enable signal generator 320 is for generating a vertical dataenable signal VDEout, and for controlling the timing which the memory310 outputs the stored pixel data. FIG. 4 shows a timing diagram ofvertical data enable signals of an image signal, before and afterextending the vertical blanking interval with an image adjustingapparatus according to the invention. In FIG. 4, T represents anincreased period in the vertical blanking interval, and a data enableduration in the vertical data enable signal VDEin added to a verticalblanking interval duration VBIin is a frame cycle of the input imagesignal Vin. Similarly, a data enable duration in the vertical dataenable signal VDEout added to a vertical blanking interval durationVBIout is a frame cycle of the output image signal Vout. In thisembodiment, the frame cycle of the input image signal equals to that ofthe output image signal Vout. As shown in FIG. 4, the vertical dataenable signal VDEout generated by the data enable signal generator 320includes a vertical data enable duration VDEout_n corresponding to ann^(th) frame, and the vertical data enable duration VDEout_ncorresponding to the n^(th) frame is largely located within a verticaldata enable duration VDEin_n corresponding to the n^(th) frame, with thevertical data enable duration VDEout_n being smaller than the verticaldata enable duration VDEin_n.

The data enable signal generator 320 generates a read signal R to thememory 310 to control when the memory 310 outputs the pixel data of theframes, such that the memory 310 respectively outputs the pixel datacorresponding to the frames during corresponding vertical data enabledurations of the vertical data enable signal VDEout. For example, thememory 310 outputs the pixel data corresponding to the n^(th) frameduring the vertical data enable duration VDEout_n, and outputs the pixeldata corresponding to the (n+1)^(th) frame during the vertical dataenable duration VDEout_n+1. In one embodiment, the vertical data enablesignal VDEout generated by the data enable signal generator 320 canserve as the read signal R, and thus the pixel data corresponding to theframes outputted by the memory 310 together with the vertical dataenable signal VDEout form the output image signal Vout.

In one embodiment, the data enable signal generator 320 can comprise acounter. When the image adjusting apparatus 300 starts receiving theinput image signal Vin to be adjusted, the counter in the data enablesignal generator 320 starts counting according to the read clock RCLK.After the period T, the data enable signal generator 320 generates adata enable duration (i.e., a high level period) in the vertical dataenable signal VDEout. After generating the data enable duration, thecounter keeps counting till reaching an end of a frame cycle P, and thena count of the counter is reset to start counting for another framecycle P. Therefore, the vertical data enable signal VDEout generated bythe data enable signal generator 320 includes cyclic data enabledurations, and between every two adjacent data enable durations is avertical blanking interval VBIout. During each data enable duration, thedata enable signal generator 320 triggers the memory 310 to output thepixel data by the read signal R. Since the read signal R is forcontrolling the timing which the memory 310 outputs pixel data of aframe, the read signal R may be utilized to control opening and shuttingof shutters of stereo glasses when the image adjusting apparatusaccording to the invention is applied for processing a 3D stereo image.

Again with reference to FIG. 4, before the pixel data of the n^(th)frame of the input image Vin is completely written into the memory 310,the image adjusting apparatus 300 starts to output the pixel data of then^(th) frame according to a relatively faster clock, and makes a timepoint at which the memory 310 finishes outputting the pixel data of then^(th) frame approximate or even equal to a time point at which thepixel data of the n^(th) frame is completely written into the memory310, thereby achieving the objective of extending vertical blankingintervals without resulting in image delay.

How the image adjusting apparatus according to the invention adjusts afrequency of the read clock and makes the output image signal Vout andthe input image signal Vin have the same frame cycles shall be describedbelow. To ensure the frame cycle of the output image signal Vout to bethe same as that of the input image signal Vin, the image adjustingapparatus 300 detects with the detector 330 a first reference point ofthe input image signal Vin and a second reference point of the outputimage signal Vout, and adjusts the frequency of the read clock accordingto the detection results. More specifically, the detector 330 detects atime point of the first reference point of the input image signal Vin togenerate a first detection signal Ir. For example, the detector 330 isan edge detector, and the first reference point is a falling edge of thevertical data enable signal VDEin of the input image signal Vin, suchthat the first detection result Ir is generated whenever the detector330 detects a falling edge in the vertical data enable signal VDEin.Similarly, the detector 330 also detects a time point of the secondreference point of the output image signal Vout. For example, the secondreference point is a falling edge of the vertical data enable signalVDEout of the output image signal, such that the second detection signalOr is generated whenever the detector 330 detects a falling edge in thevertical data enable signal VDEout.

After receiving the first detection signal Ir and the second detectionsignal Or, the adjustment value generator 340 performs analysis togenerate an appropriate adjustment value A for adjusting the frequencyof the read clock RCLK. FIG. 5 shows a functional block diagram of anadjustment value generator 340 in the image adjusting apparatus 300according to an embodiment of the invention. The adjustment valuegenerator 340 comprises a counter 510 and a determining unit 520. Uponreceiving the first detection signal Tr, the counter 510 starts countingaccording to a reference clock SCLK, e.g., a system clock of the imageadjusting apparatus 300. Upon receiving the second detection signal Or,the counter outputs a count value C to the determining unit 520, andresets the count value. The determining unit 520 determines based on thecount value C whether the frequency of the read clock RCLK is too highor too low, so as to generate a corresponding adjustment value A. Sincean appropriate frequency range of the read clock RCLK may be calculatedin advance according to a desired extended period (the period T) for thevertical blanking interval, the frequency of the write clock WCLK, andthe frame cycle of the input image signal, thus, the read clock RCLKgenerated by the clock generator 350 is supposedly quite close to atarget value. Hence, the frequency of the read clock RCLK may bedetermined as being too high or too low with an aid of a reference valueF, which may be a half of the frame cycle, for example.

FIG. 6 shows a timing diagram of vertical data enable signals of inputand output signals when the frequency of the read clock RCLK is toohigh, i.e., the read clock RCLK is too fast. When the read clock RCLK istoo fast, a time point at which pixel data of a frame is completely readout from the memory 310 is earlier than a time point at which the pixeldata of the frame is completely written into the memory, such that thecount value C generated by the counter 510 exceeds the reference valueF. FIG. 6 illustrates a situation that pixel data to be read out fromthe memory 310 is not yet written into the memory 310. Thus, when thecounter value C exceeds the reference value F, the determining unit 520determines that the frequency of the current read clock RCLK is toohigh, and accordingly generates an appropriate adjustment value A forreducing the frequency of the read clock RCLK. In contrast, when thecounter value C is smaller than the reference value F, the determiningunit 520 determines that the frequency of the current read clock RCLK istoo low, and accordingly generates an appropriate adjustment value A forincreasing the frequency of the read clock RCLK. It is to be noted thatthe above example is merely for illustrating the invention but not tolimit the invention within. In another embodiment, the counter startscounting upon receiving the second detection signal Or, and stopscounting and outputs a count value C to the determining unit 520 uponreceiving the first detection signal Ir. Accordingly, the determiningunit 520 generates an adjustment value A based on the count value C andan appropriate reference value F.

FIG. 7 shows a timing diagram of vertical data enable signals of inputand output image signals according to another embodiment of theinvention. In FIG. 7, between the vertical data enable signal VDEin andthe vertical data enable signal VDEout is a predetermined small delayperiod Y for preventing a situation that data to be read is not yetwritten into the memory 310 when the read clock is too fast. Under suchconditions, the delay time Y is also taken into considerations when theadjustment value generator 340 generates the adjustment value A. Forexample, when the determining unit 520 determines whether the frequencyof the read clock RCLK is too high or too low to generate the adjustmentvalue A, the delay time Y is subtracted from the count value C, and adifference between the two is then compared with the reference value Fto further generate an appropriate adjustment value A according to thecomparison result.

The clock generator 350 is for generating the read clock RCLK andadjusting the frequency of the read clock RCLK according to theadjustment value A. In practice, the clock generator 350 comprises aphase locked loop, for example. When the clock generator 350 firststarts to generate the read clock RCLK, the frequency range of the readclock RCLK may be calculated in advance according to the desiredextended period (the period T) for the vertical blanking interval, thefrequency of the write clock WCLK and the frame cycle of the input imagesignal Vin. More specifically, since the input image signal Vin and theoutput image signal Vout have the same frame cycle, and the number ofpixel data of each frame of the input image signal Vin is also the sameas that of the output image signal Vout, the frame cycle of the inputimage signal Vin and the output image signal Vout is represented byEquation (1):

VBIin+M/I=VBIin+T+M/O   Equation (1)

Wherein, VBIin is the vertical blanking interval of the input imagesignal, M is the number of pixel data of each frame of the input/outputimage signal, I is the frequency of the write clock WCLK, T is thedesired extended period for the vertical blanking interval, and O is thefrequency of the read clock RCLK. Further, the vertical blankinginterval VBIin of the input image signal Vin added to the extendedperiod T is equal to the vertical blanking interval VBIout of the outputimage signal Vout. Suppose the extended period T for the verticalblanking interval is represented in the frequency O of the read clockRCLK, Equation (1) is represented by Equation (2):

M/I=(N+M)/O

Wherein, N=T×O, where N represents the number of count within theextended period T when counting according to the read clock RCLK. WithEquation (1) or Equation (2), the frequency of the read clock RCLK maybe calculated in advance. The clock generator 350 then generates theread clock RCLK, which then fine tunes the read clock RCLK according tothe adjustment value A to ensure that the output image signal Vout hasthe same frame cycle as the input image signal Vin, i.e., the outputimage signal Vout is synchronized with the input image signal Vin.

With description of the above embodiments, an image adjusting apparatusand an associated method provided according to the invention effectivelyextends vertical blanking intervals of an image signal, so that anoutput image signal is synchronized with an input image signal toprevent image delay.

While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not to be limited to the aboveembodiments. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

1. An image adjusting method, comprising: providing a first image signalhaving a first data enable signal and pixel data, wherein the first dataenable signal has a first data enable duration; and generating a seconddata enable signal, wherein the second data enable signal has a seconddata enable duration; wherein, the first data enable duration and seconddata enable duration correspond to a same image frame of the first imagesignal, and the second data enable duration overlaps the first dataenable duration.
 2. The image adjusting method as claimed in claim 1,wherein the second data enable duration is smaller than the first dataenable duration.
 3. The image adjusting method as claimed in claim 1,wherein the second data enable duration starts after the first dataenable duration starts.
 4. The image adjusting method as claimed inclaim 1, wherein the pixel data of the first image signal and the seconddata enable signal form a second image signal.
 5. The image adjustingmethod as claimed in claim 4, wherein the pixel data is written into amemory during the first data enable duration.
 6. The image adjustingmethod as claimed in claim 5, wherein the pixel data is outputted fromthe memory during the second data enable duration.
 7. The imageadjusting method as claimed in claim 1, further comprising: generating acontrol signal to a pair of three-dimensional stereo glasses accordingto the second data enable signal.
 8. The image adjusting method asclaimed in claim 1, further comprising: transmitting the second dataenable signal to a pair of three-dimensional stereo glasses.
 9. An imageadjusting apparatus, for extending a vertical blanking interval of afirst image signal, the first image signal comprising a first dataenable signal and pixel data of an image frame, the first data enablesignal having a first data enable duration, the image adjustingapparatus comprising: a memory, for storing the pixel data of the firstimage signal; and a data enable signal generator, for generating asecond data enable signal and controlling when the memory outputs thepixel data; wherein, the second data enable signal includes a seconddata enable duration, the first data enable duration and the second dataenable duration correspond to the image frame, and the second dataenable duration overlaps the first data enable duration.
 10. The imageadjusting apparatus as claimed in claim 9, wherein the data enablesignal generator generates the second data enable signal according to apredetermined time, a frame cycle, and a read clock.
 11. The imageadjusting apparatus as claimed in claim 9, wherein the memory receivesand stores the pixel data during the first data enable duration.
 12. Theimage adjusting apparatus as claimed in claim 9, wherein the memoryoutputs the pixel data during the second data enable duration.
 13. Theimage adjusting apparatus as claimed in claim 9, wherein the second dataenable signal and the pixel data outputted by the memory form a secondimage signal.
 14. The image adjusting apparatus as claimed in claim 9,wherein the data enable signal generator generates a read signal tocontrol when the memory outputs the pixel data.
 15. The image adjustingapparatus as claimed in claim 14, wherein the read signal is the seconddata enable signal.
 16. The image adjusting apparatus as claimed inclaim 9, further comprising: a detector, for detecting a first referencepoint of the first data enable signal to generate a first detectionsignal, and detecting a second reference point of the second data enablesignal to generate a second detection signal; an adjustment valuegenerator, for generating an adjustment value according to the firstdetection signal and the second detection signal; and a clock generator,for generating a read clock and adjusting the read clock according tothe adjustment value.
 17. The image adjusting apparatus as claimed inclaim 16, wherein the first reference point is a first transition edgeof the first data enable signal.
 18. The image adjusting apparatus asclaimed in claim 16, wherein the second reference point is a secondtransition edge of the second data enable signal.
 19. The imageadjusting apparatus as claimed in claim 9, wherein the data enablesignal generator further generates a control signal to a pair ofthree-dimensional stereo glasses.
 20. The image adjusting apparatus asclaimed in claim 19, wherein the control signal is the second dataenable signal.